080125© M. Kostic Prof. M. Kostic Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY Effective Thermal Conductivity Errors by Assuming Unidirectional Temperature and Heat Flux Distribution Within Heterogeneous Mixtures (Nanofluids) The 5th WSEAS International Conference on HEAT and MASS TRANSFER ( WSEAS - HMT'08 ) Acapulco, Mexico, January 25-27, 2009

080125© M. Kostic Nanofluids Research: Critical Issues & Application Potentials Advanced Flow and Heat Transfer Fluids Prof. M. Kostic Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY University of Hawaii at Manoa Presented at: University of Hawaii at Manoa and Multifunctional Nanocomposite 2006 Int. Conference

080125© M. Kostic First NIU Nanofluids

080125© M. Kostic Wet-Nanotechnology: nanofluids’ applications Advanced, hybrid nanofluids: j Heat-transfer nanofluids (ANL & NIU) j Tribological nanofluids (NIU) j Surfactant and Coating nanofluids j Chemical nanofluids j Process/Extraction nanofluids j Environmental (pollution cleaning) nanofluids j Bio- and Pharmaceutical-nanofluids j Medical nanofluids (drug delivery and functional tissue-cell interaction)

080125© M. Kostic Production of Copper Nanofluids j Nanofluids with copper nanoparticles have been produced by a one-step method. j Copper is evaporated and condensed into nanoparticles by direct contact with a flowing and cooled (low-vapor-pressure) fluid. j ANL produced for the first time stable suspensions of copper nanoparticles in fluids w/o dispersants. j For some nanofluids, a small amount of thioglycolic acid (<1 vol.%) was added to stabilize nanoparticle suspension and further improve the dispersion, flow and HT characteristics. Schematic diagram of nanofluid production system designed for direct evaporation/condensation of metallic vapor into low-vapor- pressure liquids.

080125© M. Kostic Enhanced Nanofluid Thermal Conductivity j Nanofluids containing <10 nm diameter copper (Cu) nanoparticles show much higher TC enhancements than nanofluids containing metal-oxide nanoparticles of average diameter 35 nm. j Volume fraction is reduced by one order of magnitude for Cu nanoparticles as compared with oxide nanoparticles for similar TC enhancement. j The largest increase in conductivity (up to 40% at 0.3 vol.% Cu nanoparticles) was seen for a nanofluid that contained Cu nanoparticles coated with thioglycolic acid. j A German research group has also used metal nanoparticles (NPs) in fluids, but these NPs settled. The ANL innovation was depositing small and stable metal nanoparticles into base fluids by the one-step direct- evaporation method. Thermal conductivity enhancement of copper, copper oxide, and alumina particles in ethylene glycol. Appl. Phys. Lett. 78, 718, Thermal Conductivity Ratio k nf /k base Volume Fraction [%]

080125© M. Kostic Rotating drum with moving nanofluid film Insulated and vertically-adjustable boat-heater evaporator Nitrogen cooling plate with coils and fins FIG. 2: Proposed improvements for the one-step, direct-evaporation nanofluid production apparatus

080125© M. Kostic Nanofluid’s TC: Errors

080125© M. Kostic Nanofluid’s TC: CFD & Limits

080125© M. Kostic Objective :

080125© M. Kostic Conclusion (1):

080125© M. Kostic Conclusion (2)

080125© M. Kostic For further Info you may contact Prof. Kostic at: or on the Web: Prof. M. Kostic Mechanical Engineering Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY